text: var postcss = require('postcss');
  var Typography = require('typography');
  
  module.exports = postcss.plugin('postcss-typography', function (opts) {
      opts = opts || {};
  
      var typography = new Typography(opts);
  
      return function (root) {
          root.walkAtRules('typography', function (rule) {
              var css = postcss.parse(typography.toString());
              rule.replaceWith(css.nodes);
          });
      };
  });
  